[leetcode 80] Remove Duplicates from Sorted Array II

Follow up for "Remove Duplicates":
What if duplicates are allowed at most twice?

For example,
Given sorted array A = [1,1,1,2,2,3],

Your function should return length = 5, and A is now [1,1,2,2,3].

class Solution {
public:
    int removeDuplicates(int A[], int n) {
        if (n < 3) {
            return n;
        }
        int index = 1;
        for (int i = 2; i < n; i++) {
            if (A[index-1] != A[i]) {
                index++;
                A[index] = A[i];
            }
        }
        return index+1;
    }
};